Check queryset.ordered before applying enforced ordering

Author: ulgens

rest_framework/pagination.py

@@ -624,10 +624,11 @@ def paginate_queryset(self, queryset, request, view=None):
             (offset, reverse, current_position) = self.cursor
 
         # Cursor pagination always enforces an ordering.
-        if reverse:
-            queryset = queryset.order_by(*_reverse_ordering(self.ordering))
-        else:
-            queryset = queryset.order_by(*self.ordering)
+        if not queryset.ordered:
+            if reverse:
+                queryset = queryset.order_by(*_reverse_ordering(self.ordering))
+            else:
+                queryset = queryset.order_by(*self.ordering)
 
         # If we have a cursor with a fixed position then filter by that.
         if current_position is not None: